Using clips or excerpts from films, videos, or TV programs for teaching purposes is allowed in the classroom and in online education.
Showing clips or excerpts of films outside of teaching you will need to consider if your use is a fair use and apply the four factors to the number and amount of video clips being used.
According to Copyright Law for Librarians and Educators: Creative Strategies & Practical Solutions (3rd ed.) by Kenneth D. Crews, some of the points that those teaching should consider (pp. 74-75) include--
You can find out more about fair use, including online resources to help you make a fair use defense for your use, by visiting the University Library System's "What Is Fair Use?" portion of this guide.